Propeller pitch control



Sept. 2 9 2- w. s. HOOVER 2,296,348

PROPELLER PITCH CONTROL Filed May 31, 1939 2 Sheets-Sheet l INVENTORWar/2 5 51702 2 170171091" 4% 1 M ATTORNEY p 1942- w. s. HOOVER2,296,348

PROPELLER PITCH CONTROL Filed May 31, 1939 2 Sheets-Sheet 2 INVENIDR.

War/[Er 50172 2 Hauyer ATTORNEY.

Patented Sept. 22, 1942 UNITED STATES PATENT OFFICE V PROPELLER PITCHCONTROL Walter Scott Hoover, Montreal, Quebec, Canada Application May31, 1939, Serial No. 276,571

12 Claims.

This invention relates to improvements in controllable pitch propellersand has particular reference to an improved variable ratio geararrangement in the pitch changing mechanism.

An object of the invention resides in the provision of an improved geartrain.

A further object resides in the provision of a gear train in which theratio between the driving and driven element may b varied over a widerange.

A still furthenobject resides in the provision of a propeller having apower-operated element for changing the propeller blade pitch in which agear train is provided such that at selected positions a relativelylarge force and a small motion is transmitted to the blade from thepower element and at other positions a relatively small force and alarge movement is transmitted. I Other objects and advantages will bemore particularly pointed out hereinafter or may become apparent as thedescription proceeds.

These objects are obtained by the mechanism illustrated in theaccompanying drawing in which like reference numerals are used todesignate similar parts throughout. The drawings, however are for thepurpose of illustration only, and are not to be taken as limiting orrestricting the scope of th invention.

In the drawings, Fig. 1 is a longitudinal view partly in section andpartly schematic of a controllable pitch propeller and its operatingmechanism, and

Fig. 2 is a front elevational view with portions broken away of the samepropeller.

Referring to the drawings, the numeral I designates the front portion ofan engine through which a propeller shaft 12 extends. This shaft may beeither an extension of the crankshaft or may be a propeller shaft driventhrough a gear reduction. On this propeller shaft, there is mounted apropeller blade supporting, hub l4 which in the device illustratedsupports three propeller blades it. There may of course be more or fewerblades as required. On the inner end It of the propeller blade, there ismounted in driving engagement therewith a flange'member carrying on oneside thereof a bevel gear 22. This bevel gear meshes with a bevel gear24 which acts to turn bevel gear 22 and the blade l6 secured thereto tochange the blade pitch. Gear 24 is heldin position .by a bearing 26positioned on the blade hub l4 by a disk-shaped member 28 fastened tothe hub by screws 30. Splined to the gear 24 is an annular member. 32carrying an inforce supplied to the gear as is multiplied in itsapplication to the gear 34 when the gear 36 is in the position shown inFig. 2. c .When, however,

gear 36 has rotated through 180 degrees and the eccentric pivot is thenlocated nearer gear 38 than to the gear 34 then force applied to thegear 33 will be reduced in its application to the gear 34, because ofthe mechanical disadvantage but the distance through which gear' 34 willbe moved will be greater than the distance through which gear 38 ismoved. It wilLthus be seen that this gear provides a construction inwhich the r '"Eio of movement between gears 38 and gears 34 may ternalgear 34. .Meshing with the internal gear be varied as the gear 33rotates. By positioning the gear 36 so that its greatest mechanical ariavantage occurs at the point where the blade offers the greatestresistance to being turned, it; becomes possible to use a small powerunitfor turning the blade. By decreasing this mechanical advantage asthe blade moves into positions where the resistance offered to turningthe blade is less, it is possible to utilize this small power unit tothe best advantage and obtain much larger movement of the blade. Thislatterfeature attains particular usefulness as th blades approach afeathered condition where centrifugal forces acting on the blades becomeless, both due to the positionof the blade and to the necessarilyreduced speed because of the greater force required to rotate thepropeller in the feathered position.

As stated above the gear 38 may be driven by 3 any desired source ofpower. In the mechanism illustrated, a vane type motor is shown having ahousing 48 secured to the flange member 46 and the hub l4 by means ofbolts 50. 'Movable vanes 52 fit inside of the housing 48 and are splinedto a shaft 54 secured to or formed integral with gear 38. This shaft maybeisupportedin suitable bushings such as 56 in member 46 and 58 inhousing 48. Each side of the movable vane 52 is recessed to allow all toflow across the face thereof. Oil is admitted to the recess on one sidethrough an orifice 62 Orifice B2. is connected by means of a tube 64 toa channel in plug 86 which channel is in turn connected with a conduit68 leading to a governor generally indicated at 10.

Orifice 60 is connected by means of a channel outside of tube 64 to thearea inside of crankshaft 12 and with a conduit 12 also leading togovernor 10. There are as many stationary vanes I4 provided inside ofthe housing 48 as there are movable vanes 52. It is obvious that byadmitting oil under pressure to one side of the vane 52 and connectingthe other side with a drain, the vane may be moved in one direction,thus causing movement of the gear 38, while admission of oil underpressure to the other side of the vane 52 and connecting said one sidewith drain will move the vane 52 in the opposite direction, thus causinggear 38 to move in the opposite direction, thus of course changing theblade pitch in one direction or the other as desired.

The flow of oil to and from .the vane motor or other source of power maybe controlled by a manually operated valve (not shown) or may becontrolled automatically by any suitable governor such as thatdiagrammatically shown in Fig. 1.

In the structure shown in Fig. 1 a pump 16 which may be the normalengine lubricating pump or may be a pump for boosting the enginepressure or may be any suitable source of fluid under pressure suppliesfluid pressure to the conduit l8 and hence to the space between thepartitions 80 and 82 of the governor valve. The spaces on the oppositesides of the partitions are connected with the conduit 84, to a drain.The gover-' nor valve connecting the partitions 80 and 82 is actuated bythe centrifugal weights 86 and the spring 88 in accordance with thespeed of the propeller. It is obvious that movement of the governorvalve in one direction will cause one of the conduits 68, 12 to beconnected with pressure and the other with drain while movement of thevalve in the opposite direction will in effect reverse the connections.The setting of the governor may be changed by a screw 90 or any othersuitable means.

It is of course obvious that, if desired, a different form of hydraulicmotor might be used so that more than 360 degrees of movement might beimparted to the gear 38, thus reducing the size of the motor required orthe pressure of the fluid required, or both, to produce any desiredamount of pitch-changing movement of the blades.

It is to be understood that the invention is not limited to theparticular construction illustrated and described but that such changesin the size, shape and arrangement of the various parts may be resortedto as come within the scope of the subjoined claims.

Having now described the invention so that others skilled in the art mayclearly understand the same what it is desired to secure by LettersPatent is as follows:

1. In combination with a controllable pitch propeller having movablymounted blades, means for moving said blades to change their pitchangle, said means comprising a motor, and a toothed gear train having avariable gear ratio continuously drivingly connected and mechanismcontinuously, positively and drivingly connecting said gear train withsaid motor and said blades, said mechanism forming, with said geartrain, a positive and direct drive between said motor and said blades.

2. Propeller pitch changing means comprising a motor driving a gear,another gear meshing with said first mentioned gear and eccentricallyand rotatably mounted on a pivot, means for restraining said pivot fromfree circumferential movement about said first mentioned gear, means formaintaining said gears in mesh comprising a third gear meshing with saidanother gear and a propeller blade drivingly connected with said thirdgear.

3. In combination with a controllable pitch propeller having bladesrotatably held by a hub for pitch changing movements, a motor carried bysaid hub for changing the blade pitch and a gear train connecting saidmotor and said blades, said gear train comprising one gear driven bysaid motor, a second gear driving said blade and a third gear connectingsaid one and said second gears, a support for said third gearcomprising, a pivot eccentrically located in said third gear and meansconnecting said pivot with said hub.

4. In combination with a controllable pitch propeller having bladesrotatably held for pitch changing movements in a hub, a motor can'ied bysaid hub for changing the blade pitch and a gear train connecting saidmotor and said blades, said gear train comprising one gear driven bysaid motor, a second gear driving said blade and a third gear connectingsaid one and said second gears, a support for said third gear comprisinga pivot eccentrically located in said third gear and a link attachedadjacent one end to said pivot and pivoted adjacent the other end tosaid hub to permit substantially free movement of said pivotsubstantially radially of said one gear but preventing free movement. ofsaid pivot circumferentially of said one gear.

5. In combination with a controllable pitch propeller having movablymounted blades, a motor rotatable with said propeller, a gear trainconnecting said motor and said propeller, said gear train comprising aninternal and an external gear and a third gear meshing with saidinternal and external gears, a pivot rotatable with said propeller,means for preventing said pivot from moving freely circumferentially ofsaid internal and external gears but permitting movement of said pivotbetween said internal and external gears and means eccentric to saidthird gear rotatably connecting said pivot and said ear.

6. In combination with a controllable pitch propeller having bladesrotatably held by a hub for pitch changing movements, constructed andarranged so that as the blade pitch changes the force required to turnthe blade changes, means for supplying a substantially uniform force forturning said blades and a variable ratio'gear train carried entirely bysaid hub and continuously drivingly connecting said force supplyingmeans and said blades for varying the effective force applied to saidblades by said means durin pitch changing movements.

7. In combination with a controllable pitch propeller having bladesrotatably held in a hub for pitch changing movements, constructed andarranged so that as the blade pitch changes the force required to turnthe blade changes, means i for supplying a substantially uniform forcefor turning said blades and a variable ratio gear train for continuouslyvarying the effective force applied to said blades by said means duringpitch changing movements said variable ratio gear train comprising anexternal gear, an internal gear, concentric with said external gear, anda third gear connecting said internal and external gears, said thirdgear rotatably mounted to turn about a point eccentric to itscircumference and means connecting said gear mounting with said hub torestrain said gear from free bodily movement relative to said hub and tocause said external gear when turned to transmit force through saidthird gear to said internal gear.

8. In combination with a controllable pitch propeller having blades heldby a hub for pitch changing movements, constructed and arranged so thatas the blades change pitch from a predetermined position the forcerequired to turn them becomes less, a motor for supplying force tochange the blade pitch, a gear train with a variable ratio connectingsaid motor and said blades, said gear train having a drive gear, adriven gear and a third gear mounted on a pivot and connecting saiddrive and driven gears, said pivot arranged eccentric of said third gearand movable toward and from said drive and driven gears as said thirdgear is rotated, said gears and said blades relatively positioned sothat when the blade is in said predetermined position said pivot is in aposition toward said driven gears.

9. In combination with a controllable pitch propeller having movablymounted blades, an hydraulic motor for moving said blades to changetheir pitch angle, a source of hydraulic fluid under substantiallyconstant presure for supplying said motor with a substantially uniformturning force and a gear trainhaving an automatically variable gearratio drivingly connected between said motor and said blades, said gearratio being varied automatically as the gears are turned and meansmovable by the rotation of the gears for varying said ratio.

10. In combination, propeller blades rotatably held by a hub for pitchchanging movements,

and constructed and arranged so that as the blade pitch angle is changedduring operation of the propeller, the force required to turn the bladesto change their pitch angle varies, a motor for moving said blades tochange their pitch angle, said motor exerting a substantially uniformforce, a variable ratio gear train, having a definite and differentratio for each successive position of the gears of said train and theblades moved thereby, connecting said motor and said blades for varyingthe effectiveforce exerted by said motor on said blades as the bladesare turned by said motor, said gear train constructed and arranged sothat said effective force varies in the same. direction as the forcerequired to turn saidblades to thereby give a large effective turningforce when a large force is required to turn said blades.

11. In combination, propeller blades movably mounted for pitch changingmovements, constructed and arranged so that as the blade pitch angle ischanged from one pitch to another such as from substantially fiat pitchto substantially feathered position the force required to move theblades first increases and then decreases, a motor for exerting asubstantially uniform force for moving said blades, a gear traincontinuously connecting said motor with said blades and moving saidblades whenever said motor moves,

means for automatically varying the ratio and mechanical advantage ofsaid gear train as the I gears turn, said means constructed and arrangedso that as the gears are turned to move the blades the uniform force ofsaid motor is transformed through said variable ratio gear train to aforce at said blade which first increases and then decreasessubstantially in time with the increase and decrease of the forcerequired to move said blades.

12. In combination with a controllable pitch propeller having bladesrotatably held, by a hub for pitch changing movements,constructed andarranged so that as the blade pitch changes the force required to turnthe blade changes, means for supplying a substantially uniform force forturning said blades and a variable ratio gear train having a diflerentratio for each successive position of the gears of said train andconnect ing said force supplying means and said blades for continuouslyvarying the eifective force applied to said blades by said means duringpitch changing movements.

WALTER SCOTT HOOVER.

